libxl: provide xenlight.pc

A pkg-config file for libxl. It also contains two variables
(xenfirmwaredir and libexec_bin) so that tools that are very keen on
knowing the locations of Xen binaries (say, libvirt) can use them to
determine the location of the binaries.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
[ ijc -- ran autogen.sh ]

configure

@@ -604,6 +604,7 @@ SHAREDIR
 XEN_LIB_STORED
 XEN_LOG_DIR
 XEN_RUN_DIR
+XENFIRMWAREDIR
 LIBEXEC_BIN
 CONFIG_LEAF_DIR
 host_os
@@ -1930,6 +1931,9 @@ libexecdir=`eval echo $libexecdir`
 LIBEXEC_BIN=`eval echo $libexecdir/$PACKAGE_TARNAME/bin`
 
 
+XENFIRMWAREDIR=`eval echo $libexecdir/$PACKAGE_TARNAME/boot`
+
+
 XEN_RUN_DIR=$localstatedir/run/xen